As discussed in the co-pending Patent Application corresponding to Provisional Application 61/299,652 filed Jan. 29, 2010, it is possible to detect the presence of explosives or contraband utilizing nuclear quadrupole resonance. In this application a detected substance is irradiated with low frequency energy in the 0.1-5 MHz band which corresponds to a spectral line of the material to be detected. The resulting stimulated emission is indicative of the presence of the material, with the material being irradiated utilizing a terminated balanced transmission line.
The range of such systems from the balanced transmission line is limited. Also, the transmission lines are relatively long and in some cases are provided in the form of a balanced transmission line grid or matrix.
While it is possible to detect materials of interest at short distances from the grid or transmission line, long range detection techniques are required.
There is therefore a necessity for being able to detect the stimulated emission spectra of explosives or contraband at large distances from a detection point. For instance, it is desirable to be able to scan a crowd and detect the presence of explosives or contraband carried by an individual at some distance from a detection point.
It is also desirable for instance to be able to detect explosives or contraband carried in vehicles which may be at some distance from a detection point; and to do so in a stealthy manner.
It is noted that for 0.1-5 MHz, the antennas associated with such frequencies are exceedingly large. Also long are the terminated balanced transmission lines which need to be in place prior to the detection of explosives or contrabands.
Moreover, in an application when one is seeking to drive a vehicle down a road, one wants to be able to detect the presence of explosives ahead or beside the vehicle. Vehicles in general cannot conveniently carry antennas that are resonant at the low MHz frequencies very easily because of their size. There is therefore a need to provide a compact portable system for detecting explosives or contraband at a distance without having to use antennas whose quarter wavelengths are on the order of hundreds of feet.
In short, there is a need for long range detection of the stimulated emission from material caused by the absorption of 0.1-5 MHz energy.